1. Field of the Invention
Embodiments of the present invention are generally related to embodiments of the present invention relate to fiber stretcher modules for use in the 1550 nm wavelength range. More specifically, embodiments of the present invention relate to a fiber stretcher module for dispersion management in short pulse laser systems.
2. Description of the Related Art
A fiber stretcher module offers a solution for known femtosecond fiber based chirped pulse amplification systems that typically use bulk optics or a chirped fiber Bragg grating to stretch the pulses. A chirped fiber Bragg grating generally yields large group delay ripples as well as significant amplitude ripples which are highly undesirable. As such, fiber-based stretchers are preferable over stretchers made of bulk optics due to smaller size, better stability, longer lifetime, lower cost and improved characteristics over the drawbacks described above.
A difficulty with using a fiber stretcher is that it must match a particular compressor grating (i.e., it must have an equal quantitative dispersion with an opposite sign—that is, positive/negative). Generally, the compressor grating has high numerical values for both third order dispersion β3 and fourth order dispersion β4. For example, a 1200 lines/mm compressor grating working at an incidence angle of 64.5° with a second order dispersion of β2=−57.4 ps2 at 1550 nm should have the below dispersion values:
β2=−57.4 ps2; β3=3.17 ps3; and β4=−0.291 ps4 
At 1550 nm, these values correspond to:
D=45 ps/nm; RDS=0.0420 nm−1; and RDC=0.00295 nm−2 
Where D is the dispersion, RDS is the relative dispersion slope, and RDC is the relative dispersion curvature of the grating.
However, using a known stretcher module made of a combination of an existing Dispersion Compensation Fiber (DCF) and Super Large Effective Area (SLA) fiber, i.e., using around 0.90 km of Ultra-High Slope (UHS) DCF and 3.6 km of SLA, a stretcher module with the below dispersion values at 1550 nm can be made:
β2=57.2 ps2; β3=−3.17 ps3; and β4=0.14 ps4 
While it is observed that β2 and β3 are very close to target, β4 is ˜50% of matching that of the desired grating. As such, a new solution is needed achieve the desired match between the stretcher module and a chosen grating.